Metal working processes include cutting, grinding, roll forming, forging, pressing, punching, rolling and the like, and such types of metal working are usually carried out using lubricating oils. In cutting and grinding, for example, it is common to employ cutting and grinding oils for the purpose of extending the life of working tools such as drills, end mills, cutting tools, grinding wheels and the like, improving the surface roughness of working surfaces and raising productivity in mechanical working by increasing machining performance.
Conventional oils for metal working employ large amounts of chlorine-based extreme pressure agents such as chlorinated paraffin and sulfur-based extreme pressure agents such as sulfidized oils and polysulfides. The use of chlorine-based extreme pressure agents is considered indispensable particularly for difficult machining such as shaving, deep hole boring (BTA working, gun drill working), automatic lathe working, broaching and screw roll forming or heavy machining, or for machining of difficult-to-cut materials and/or difficult-to-grind materials such as heat-resistant alloys including stainless steel or inconel.
In recent years, however, concerns have been raised regarding carcinogenicity of the chlorine-based extreme pressure agents contained in oils for metal working, or regarding generation of dioxin by thermal disposal of chlorine-based waste solutions, and therefore it has been desired to develop metal working techniques that do not employ chlorine-based extreme pressure agents.
Development of new oils for metal working that do not employ chlorine-based extreme pressure agents is progressing as a way of satisfying this demand, and for example, the use of oils for metal working that combine sulfur-based extreme pressure agents and sulfonates has been proposed (for example, see Patent document 1).
On the other hand, there have also been developed cutting/grinding methods with minimal quantity lubricant systems whereby a trace amount of oil at about 1/100,000-1/1,000,000 of the amount of oil used for conventional cutting and grinding is supplied to the working part together with a compressed fluid (for example, compressed air) for cutting and grinding. In such systems, a cooling effect is achieved due to the compressed air, and the trace amount of oil used allows the amount of waste to be reduced, thereby resulting in improvement in the effect on the environment that is caused by large-scale emission of waste products (for example, see Patent document 2).    [Patent document 1] Japanese Unexamined Patent Publication HEI No. 6-158074    [Patent document 2] WO02/081605